The Oil in the Machine

In Chapter 19, Larry Harris breaks down the most overused word in finance: Liquidity. Everyone wants it, but very few people can define it.

Harris says liquidity is the successful outcome of a Bilateral Search. You are looking for a seller, and a seller is looking for you. When you find each other, you’ve found liquidity.

The Four Dimensions of Liquidity

Liquidity isn’t a single number. It has four distinct “faces,” and depending on who you are, some matter more than others.

1. Immediacy: How fast can you trade? If you need to trade now, you are demanding immediacy. This is what market orders are for.
2. Width (or Breadth): What is the cost? This is usually the bid/ask spread. If the spread is 1 cent, the market is “narrow.” If it’s 50 cents, it’s “wide.”
3. Depth: How much can you trade? A market might have a 1-cent spread, but if there are only 100 shares available at that price, it has no “depth.” If you want to buy 10,000 shares, you’ll have to pay more.
4. Resiliency: How fast does the price bounce back? If a big seller dumps a million shares and the price drops from $100 to $95, does it stay there? Or do value traders step in and push it back to $100 in five minutes? That “bounce back” is resiliency.

Who Supplies the Liquid?

We’ve met these characters before, but now we see how they fit into the search problem:

• Market Makers: They supply Immediacy for small orders.
• Block Dealers: They supply Depth for the big institutional whales.
• Value Traders: They supply Resiliency. They are the “buyers of last resort” who step in when everyone else is panicking.
• Arbitrageurs: They are the Porters. They don’t create liquidity; they move it from one market to another (e.g., New York to London).

The Trade-off

You can’t have everything.

• If you want Immediacy, you usually have to give up Width (you pay a higher cost).
• If you want a Good Price (Width), you usually have to give up Immediacy (you have to wait with a limit order).
• If you want Depth, you have to give up Immediacy AND Width.

Summary: Liquidity is a Service

Think of liquidity like a taxi service.

• The Market Makers are the drivers waiting at the stand (Immediacy).
• The Spread is the fare you pay.
• The Depth is how many taxis are available.

If there are no taxis, you have to walk (wait for a limit order to fill). If there are too many people and not enough taxis, the fare goes up (the spread widens).

Next time, we’ll look at the other side of the coin: Volatility.

Next Post: Volatility: The Random Walk and the Noise